This invention relates to a method for compensating for an output of a semiconductor luminous device and an apparatus therefor, and more particularly to a method for compensating for a variation in optical output of a semiconductor luminous device for outputting an optical signal to an optical fiber due to both a variation in ambient temperature and a change of the semiconductor luminous device with time.
An output of a semiconductor luminous device for outputting an optical signal to an optical fiber is varied due to a variation in ambient temperature and a deterioration of the device due to an increase in ambient temperature and with time. A variation of output of the semiconductor due to a variation in ambient temperature has been conventionally subjected to compensation. However, the prior art fails to compensate for a deterioration in output of the device due to a variation in ambient temperature and with time.
Thus, the prior art fails to satisfactorily compensate for a reduction in luminous output of the semiconductor luminous device.
The present invention has been made in view of the foregoing disadvantage of the prior art.
It is an object of the present invention to provide a method for compensating for an output of a semiconductor luminous device which is capable of facilitating temperature compensation for the semiconductor luminous device and deterioration compensation therefor.
It is another object of the present invention to provide a method for compensating for an output of a semiconductor luminous device which is capable of raising an alarm indicating that a life of the semiconductor luminous device is nearing an end.
It is a further object of the present invention to provide a method for compensating for an output of a semiconductor luminous device which is capable of effectively preventing breakage of the semiconductor luminous device by both temperature compensation for the semiconductor luminous device and deterioration compensation therefor.
It is still another object of the present invention to provide an apparatus for compensating for an output of a semiconductor luminous device which is capable of facilitating temperature compensation for the semiconductor luminous device and deterioration compensation therefor.
It is yet another object of the present invention to provide an apparatus for compensating for an output of a semiconductor luminous device which is capable of raising an alarm indicating that a life of the semiconductor luminous device is nearing an end.
It is a still further object of the present invention to provide an apparatus for compensating for an output of a semiconductor luminous device which is capable of effectively preventing breakage of the semiconductor luminous device by both temperature compensation for the semiconductor luminous device and deterioration compensation therefor.
In accordance with one aspect of the present invention, there is provided a method for compensating for an output of a semiconductor luminous device for outputting an optical signal to an optical fiber wherein an output variation quantity of the semiconductor luminous device due to a variation in ambient temperature is provided, to thereby adjust a drive current of the semiconductor luminous device, resulting in being compensated for. The method includes the steps of operating an output reduction of the semiconductor luminous device per unit time owing to a deterioration of the semiconductor luminous device depending on a current fed to the semiconductor luminous device and the ambient temperature and obtaining an output reduction quantity of the semiconductor luminous device based on a life of the semiconductor luminous device using a cumulative value of the output reduction. The method also includes the step of adjusting the drive current on the basis of the output variation quantity and the output reduction quantity. Such construction permits compensation for both an output reduction of the semiconductor luminous device due to a deterioration in characteristics of the semiconductor luminous device and an output reduction thereof due to a temperature variation, to thereby ensure that the semiconductor luminous device may exhibit a constant performance over a long period of time.
In a preferred embodiment of the present invention, the method further includes the step of comparing the output reduction quantity with a reference value predetermined depending on the semiconductor luminous device, to thereby make judgment that a life of the semiconductor luminous device is nearing an end, resulting in raising an alarm when the output reduction quantity exceeds the reference value. Such a step permits the fact that the semiconductor luminous device is nearing an end of a life thereof to be effectively indicated, so that the semiconductor luminous device may be safely replaced with a new one.
In a preferred embodiment of the present invention, the method may further include the steps of operating an added value obtained by addition between the output variation quantity and the output reduction quantity and restricting the added value so that the drive current of the semiconductor luminous device determined depending on a current command value for commanding the drive current and the added value may be at a level of a rated feed current of the semiconductor luminous device or below. Also, the method may further include the step of raising an alarm when a duration during which the drive current is kept at the predetermined constant level reaches or exceeds a predetermined period of time. Such construction effectively prevents flowing of a large current (or a current larger than the rated feed current) through the semiconductor luminous device which promotes a deterioration of the semiconductor luminous device.
In accordance with another aspect of the present invention, there is provided an output compensation apparatus for a semiconductor luminous device for outputting an optical signal to an optical fiber, which generally includes a semiconductor drive circuit for feeding the semiconductor luminous device with a drive current on the basis of a current command value, a temperature sensor for detecting an ambient temperature of the semiconductor luminous device, a temperature compensation means for providing an output variation quantity of the semiconductor luminous device depending on a variation in the ambient temperature using an output of the temperature sensor, an addition point for adding a compensation quantity based on the output variation quantity to the current command value to provide an added value and feedback it to the semiconductor drive circuit. The output compensation apparatus is featured in that it includes a life-based reduction operation means for operating an output reduction of the semiconductor luminous device per unit time owing to a deterioration of the semiconductor luminous device depending on a current fed to the semiconductor luminous device and the ambient temperature to provide an output reduction quantity of the semiconductor luminous device based on a life thereof using a cumulative value of the output reduction, and an addition means for adding the output variation quantity and the output reduction quantity to each other to provide the compensation quantity. Use of the compensation quantity thus obtained permits the apparatus to compensate for an output reduction of the semiconductor luminous device due to a variation in ambient temperature and a deterioration in characteristics of the semiconductor luminous device while being significantly reduced in manufacturing cost thereof.
In a preferred embodiment of the present invention, the life-based reduction operation means includes an output reduction operation means for operating an output reduction of the semiconductor luminous device per unit time owing to a deterioration of the semiconductor luminous device depending on the current command value fed to the current drive circuit and an output of the temperature sensor, as well as an output reduction quantity operation means for accumulating an output of the output reduction operation means to provide the output reduction quantity. Such configuration likewise permits the output compensation apparatus to compensate for an output reduction of the semiconductor luminous device due to a variation in ambient temperature and a deterioration of the semiconductor luminous device while being significantly reduced in manufacturing cost thereof.
In a preferred embodiment of the present invention, the output compensation apparatus also includes a life judging means for comparing the output reduction quantity with a reference value predetermined depending on the semiconductor luminous device, to thereby make judgment that a life of the semiconductor luminous device is nearing an end, resulting in raising an alarm when the output reduction quantity exceeds the reference value. Such construction permits the output compensation apparatus to positively inform in an early stage that a life of the semiconductor luminous device is nearing an end due to the ambient temperature and a deterioration of the semiconductor luminous device while being significantly reduced in manufacturing cost thereof.
In a preferred embodiment of the present invention, the output compensation apparatus also includes a limiter for subjecting an added value obtained by addition between the output variation quantity and the output reduction quantity to restriction so that the drive current of the semiconductor luminous device determined depending on a current command value for commanding the drive current and the added value exceeds a level of a rated feed current of the semiconductor luminous device. The limiter may be constructed so as to raise an alarm when a duration during which the drive current is kept at the predetermined constant level reaches or exceeds a predetermined period of time. Such configuration minimizes a reduction in life of the semiconductor luminous device due to an excessive increase in drive current for compensating for an output reduction of the semiconductor luminous device due to the ambient atmosphere and a deterioration of the device while significantly reducing a manufacturing cost of the device.